Influence of Heat Treatment at 550–810°C on Inter- and Intragrain Critical Currents of Bi,Pb-2223 Ceramics

Abstract

The degradation of the superconducting phase Bi_1.65Pb_0.35Sr_1.8Ca_2.2Cu₃O_y and its characteristics: electrical resistivity R, critical temperature T_c (R=0), critical current density j_c, and volume fraction of Meissner phase Cm, have been investigated at 550–810°C and P_O2=2·10¹·1·10⁵ Pa by X-ray diffraction, resistance, inductance and magnetic methods. It was established that at P_O2≥10³ Pa degradation of the ceramic samples runs through the solid solutions decomposition. As a result, the intergrain critical current is decreased 10–20 times while the intragrain one is increased 1.5–2 times. At P_O2=10¹−10² Pa the inter- and intragrain critical currents are decreased by 5–10 times and by 1.5–2 times respectively as a result of oxygen extraction without visible destruction of the Bi,Pb-2223 structure.